Yeah, the major problem with the web is the fact that even if the latest versions of MS and NS end up being totally compatible, programmers still have to deal with the fact that a large percentage of people out there are using older versions. So currently the situation is that you have to go with the lowest common denominator, or just live with the fact that some people won't see your pages the way you want them to.. It's really frustrating.. sometimes leads to having to code 2 or more versions of the same site, just to make everything work. Grrr.. Bad MS, Bad NS..
Interesting factet.. Did you know that when creating the sydney 2000 olympics website, IBM accidentally forgot to put all the ALT tags in the images? Someone using a voice browser reported them to the olympic commission or someone (I forget) and IBM quoted something like 12 months and 2 million dollars to put them all in.. Unbelievable right?
The moral of this tale is, umm, try and make your pages as accessible to as many people as possible, and maybe write a script to test for people using versions 2.0 or less of browsers and give them mean messages..